1. Field of the Invention
The invention concerns a video endoscopic probe with a distal color CCD sensor. The technical field of the invention is that of endoscopy devices.
The term "video endoscopy" designates an examination which allows one to obtain on a television monitor the image of a target situated inside of a dark cavity into which the distal end of a video endoscopic probe has been introduced.
2. Discussion of Background Information
Among the known devices pertaining to color video endoscopy, it is possible to distinguish two types of video endoscopes. The first type covers devices in which the image of the target observed inside of a cavity is transmitted by an endoscope or a fibroscope to a color CCD sensor situated outside of the cavity. This first type of video endoscope corresponds in particular to cameras are color CCD sensor equipped with a focussing objective and a mechanical connection device allowing the objective of said camera to be locked on the cup surrounding the eyepiece of an endoscope or fibroscope, this camera is connected by an umbilical cable to an external video processor which generates a video signal which signal can be viewed directly on a color monitor.
The second type of video endoscope covers devices in which the CCD sensor is housed directly in the distal end of the video endoscopic probe. The sensor is therefore introduced inside of the cavity in which the target to be examined is situated. Among the devices arising from this second type of embodiment, it is possible to distinguish two categories of video endoscopes with a distal CCD sensor capable of delivering color video images.
The first category covers devices in which the CCD sensor is a "monochromic" sensor (also called "black and white" sensor) which delivers an electrical signal containing only the luminance information. In this case, obtaining a video signal which can be viewed on a color monitor requires an illumination device which can sequentially deliver flashes corresponding to the three primary colors, a device for picking up the video signals generated sequentially by the monochromic distal CCD sensor during the flashes, and a processor which makes it possible to continually store the last three monochromic video frames in memory and to reconstitute a video signal which can be utilized directly on a color monitor from the three monochromic frames available in memory.
The second category of video endoscopes with distal CCD sensor covers devices in which the CCD sensor is a "trichromic sensor" (also called "color" sensor) which, in association with an illumination device which delivers a permanent and continuous white light, provides an electrical signal containing the luminance and chrominance information. This signal is transmitted to a processor which generates a video signal which can be directly viewed on a color monitor.
The difficulties in designing a video endoscope with a distal CCD sensor result essentially from the diversity of the applications requiring a range of probes whose useful lengths can range between 20 cm (for a dental probe) and 50 m (for a tubing inspection probe), and therefore from the need to adapt the characteristics of the video processor, as a function of the length of the electrical cable connecting the processor to the distal CCD sensor.
The joint functioning of a color CCD sensor, and of the video processor with which it is associated, in effect proceeds essentially from correct management of the phase shifts of the different high-speed clocks (14.2 MHZ in standard PAL) which are generated by the processor and described hereinafter.
"Pixel" clocks--This relates to clocks transmitted to the distal CCD sensor, in which they are used, on the one hand, for synchronizing the reading of the electrical voltages contained in the unit cells (called pixels) of the light-sensitive layer of the sensor and, on the other hand, for extracting from these unit voltages the significant information which, after integration, will constitute the electrical signal delivered by the CCD sensor and transmitted to the video processor.
"Sampling" clock--This relates to a clock used locally for synchronizing the sampling by the video processor of the electrical signal generated by the CCD sensor and transmitted to the processor. The proper functioning of the processor necessarily requires that the sampling clock be completely in phase with the incident electrical signal. Given the length of the electrical connections connecting the sensor to the video processor with which it is associated, misalignment of the color CCD sensor in the distal end of the video endoscopic probe introduces a redhibitory phase shift at the level of the processor between the sampling clock and the incident electrical signal. A phase shift results from the running total of the transmission delay to the CCD sensor of the pixel clocks generated by the video processor and the transmission delay to the video processor of the electrical signal generated by the CCD sensor. The method of remedying such a dysfunction consists of delaying either the sampling clock or the pixel clocks transmitted to the distal CCD sensor by the video processor, and in this way compensating for the overall phase shift mentioned above. The modalities of implementation of one or the other of these delay devices, and the connection problems proceeding from them, vary as a function of the integration mode of the video processor which can, depending on the architecture used, be external to the video endoscopic probe with distal CCD sensor or an integral part of the probe.
The video endoscopes arising from the first type of architecture utilize a case generally combining a light generator and a video processor. It is this case on which the connection device connected with the proximal end of the umbilical cable of the video endoscopic probes with distal CCD sensor is connected. The interchangeability of the different probe models which can be connected to the same processor obviously assumes a complete compatibility between the processor and the probes, and therefore integration in each probe of a specific delay device.
For example, the video endoscopic probes with distal monochromic CCD sensor described in U.S. Pat. No. 4,539,586 (Welch Allyn, September 1985) are equipped with a connection box allowing the probes to be connected on the case merging a generator of trichromic flashes and a video processor. This connection box contains two devices allowing adjustment of the characteristics of the two pixel clocks provided by the video processor and transmitted to the distal monochromic CCD sensor. An amplifier allows for adjustment of the level of the electrical signal generated by the distal monochromic CCD sensor, and transmitted to the video processor.
European Patent 0 218 226 B1 (Olympus, October 1986) describes a video processor which has a synchronization generator capable of delivering several sampling clock types corresponding to the number of endoscopic probe models having a distal CCD sensor, the connectors of the probes contain an electronic key which, when suitably decoded by the processor, allows the processor to select automatically the sampling clock suited to the connected probe.
U.S. Pat. No. 5,434,615 (Fuji Optical, July 1995) describes a video endoscopic probe with distal color CCD sensor having a control handle in which is housed the sampler, normally associated with the video processor, and an umbilical cable whose proximal end is equipped with a connection box in which the sampling clock generator is housed. The clock has a delay which is suited to the characteristics of the probe in consideration. The probe is connected to an external video processor which directly receives the electrical signal delivered by the sampler housed in the control handle of the probe. The probe utilizes synchronizing by the sampling clock generator which housed in the connector of the probe.
Outside of the particular configurations described in the patents mentioned above, the video endoscopic probes which can be connected on an external video processor most often have a delay device integrated in the connector or in the handle of said probe and which acts on the pixel clocks generated by the video processor and transmitted to the distal color CCD sensor. In any case, the main technical disadvantage inherent to this first type of architecture lies in the break of continuity introduced by the connection of the probe, of the electrical connection (conductors and braided ground strap) bringing to the video processor the electrical signal generated by the distal color CCD sensor, electrical signal whose transport proves to be delicate because of its low level as well as its wide pass band. It is also appropriate to note that, even if this type of architecture allows for delaying the pixel clock signals transmitted by a video processor to a distal color CCD sensor in such a way as to make video endoscopic probes of different lengths compatible with the same processor, it does not, for all that, make corrections which would allow compensation for the statistical dispersion of the characteristics of the color CCD sensors implemented in the probes.
The disadvantages mentioned above have been eliminated in the video endoscopes arising from the second type of architecture mentioned above, and in which each video endoscopic probe with distal color CCD sensor has its own video processor, these probes being connected to an external case merging a light fixture and having a device which delivers the various voltages for the electrical supply of the video processor. It is thus possible under these conditions for each processor to be completely adjusted as a function of the length of the probe in which it is integrated (adjustment of the delay of the sampling clock or of the delay of the pixel clocks), as well as a function of the specific characteristics of the distal CCD sensor with which it is associated (adjustments of colorimetry allowing to correct the dispersion of the parameters of the CCD sensor).
Thus, U.S. Pat. Nos. 5,701,155 (Welch Allyn, December 1997) and 5,441,043 (Welch Allyn, September 1992), and European Patents 0 587 514 A1 (Welch Allyn, September 1993) and 0 587 512 A2 (Welch Allyn, September 1993) describe video endoscopic probes having a distal color CCD sensor which is equipped with a connection box connected with the proximal end of the umbilical cable of the probes and which is used as housing for a video processor. The box is equipped with a composite connector which is connected on an external box combining a light fixture, the electrical supply for the video processor integrated in the connection box, and allows the case to be connected to a color video monitor. The main drawback inherent to the concept described in these patents results from the need to connect the video endoscopic probe with distal color CCD sensor, to a specific external case in which a light fixture in particular is housed, on whose color temperature is fixedly set the device for the white balance adjustment of the video processors integrated in the probe connectors. This solution prohibits the user from choosing the light source which is implemented.
In any case, the connection device connected with the proximal end of the umbilical cable of a video endoscopic probe with distal CCD sensor must, under these conditions, simultaneously ensure the continuity of a certain number of electrical connections and the transmission to a bundle of optical fibers of the light emitted by a light fixture. The connection of video endoscopic probes which can be connected on a single case (merging light fixture and electrical supply devices, or light fixture and video processor) will generally have a "composite" structure different from the "Y-shaped" structure of the connection devices of probes which can be connected on two distinct cases (for example, a light generator and a video processor).
The six patents mentioned hereinafter relate to connection devices allowing to connect video endoscopic probes with distal CCD sensor to a single external case.
European Patent EP 0 131 971 B1 (Olympus, July 1984) describes a fibroscope connection device capable of ensuring simultaneously the continuity of a light connection and of several electrical connections. This device could therefore be easily adapted to a video endoscopic probe with distal CCD sensor. The device is made up of a cylindrically shaped connector with an axial fibered terminal and several lateral electrical connection pins distributed in an annular manner around the end of said connector.
U.S. Pat. No. 4,539,586 (Welch Allyn, September 1985) describes a box integral with the proximal end of the umbilical cable of a video endoscopic probe with a distal monochromic CCD sensor and utilizes an integrated electronic board which is adapted to ensuring the interchangeability of the probes. The proximal side of the box has a series of connectors allowing it to connect simultaneously a light connection and several connections of electrical or pneumatic nature. The particularity of this patent lies in the fact that it describes simultaneously the principle of a composite connector and the integration of an electronic circuit in said connector, a concept which has been used again in U.S. Pat. Nos. 5,701,155 (Welch Allyn, December 1997) and 5,441,043 (Welch Allyn, September 1992), and European Patents 0 587 512 A2 (Welch Allyn, September 1993) and 0 587 514 A1 (Welch Allyn, September 1993) which relate to endoscopic probes with a distal color CCD sensor equipped with a composite connection box in which a video processor is integrated. The connection mode described above has been used in particular by the company Welch Allyn (System 2000 and System XT) and by the company Pentax (System EPM 3000).
European Patent EP 0 730 844 A1 (Olympus, September 1996) describes a connection device allowing it to associate a video endoscopic probe with distal color CCD sensor with two distinct cases, and therefore all the more so with a single case. The device consists of one cylindrical connector equipped with an axial fibered terminal which is plugged directly into the connecting coupling of a light generator. This connector has a lateral multipin electrical connection coupling on which a multiconductor electrical cable is connected. The other end is plugged into the connection coupling of a video processor. The drawback of such a connection device, which is implemented by the company Olympus (System Evis 100), lies in the multiplicity of the connections affecting the electrical linkages, certain ones of which transmit electrical signals which have simultaneously a low level and a wide pass band. Other variants of connection devices allowing to associate a video endoscopic probe with distal color CCD sensor with two distinct cases have also been implemented by the company Olympus; these variants consisting either of fixedly associating a lighting connecting strap with an electrical connector, or of fixedly associating an electrical connecting strap with a lighting connector.
The use of a video endoscopic probe with distal color CCD sensor obviously assumes that the image of the target situated in front of the distal end of the probe is displayed on a color video monitor. This monitor is most often connected on the external case associated with said probe. The recent miniaturization of LCD technology video screens has enabled the consideration of the integration of a video monitor with a small space requirement in the control handle of a video endoscopic probe with a distal color CCD sensor. A color video monitor integrated in the control handle can be used for purposes other than the simple display of the video image delivered by the video endoscopic probe with distal color CCD sensor. For example; U.S. Pat. No. 5,373,317 (Welch Allyn, December 1994) describes a video endoscopic probe with a distal color CCD sensor whose control handle has a color video monitor and a control joystick. The joystick can be used either for controlling an electrical motorization system integrated in the handle and adapted for modifying the orientation of the distal articulated prop of the probe, or for moving indexes in the image displayed by the video monitor. This allows for the managing of a program for processing the image displayed on the monitor. The aesthetic appearance of such a control handle having an integrated video monitor and a joystick for control of the prop is described in the U.S. Pat. No. DES.358471 (Welch Allyn, May 1995). These two patents mentioned above have been implemented in the video endoscopic probes of the System XT developed by Welch Allyn, probes whose electronic structure corresponds to European Patent 0 587 514 A1 (Welch Allyn, September 1993). In any case, the integration of a color video monitor in the control handle of a video endoscopic probe with distal color CCD sensor assumes under these conditions the integration, in the umbilical cable integral with said handle, of additional electrical connections between the video processor and the handle, connections which are adapted for providing the monitor with the video signal and the supply voltages necessary for its functioning.